1. Field of the Invention
The present invention relates generally to systems and methods which are used in electrochemical analysis. More particularly, the present invention relates to electrochemical instruments and methods which are used to analyze the ionic activity fluids in a wide variety of laboratories including clinical laboratories and other healthcare facilities.
2. Description of the Related Art
Clinical chemistry involves the qualitative and quantitative analyses of body fluids, such as blood, urine, spinal fluid and other materials. Clinical chemistry encompasses multiple specialty testing areas including coagulation, hematology, immunochemistry, as well as chemistry. The test results derived from such analyses are used by physicians and other healthcare professionals to diagnose, monitor and treat diseases. The analysis protocols, instrumentation and other equipment utilized in clinical laboratory testing must be capable of providing accurate and repeatable test results. In addition, it is desirable that the procedures and instrumentation be simple and efficient. The testing equipment and procedures should be versatile enough that they can be used in healthcare locations where relatively few samples are tested as well as in larger clinical laboratories where the number of samples being tested on a daily basis is quite large.
A wide variety of analysis protocols are based on electrochemical analysis of the fluid being tested or the reaction product(s) of the fluid and one or more reagents. The majority of electrochemical procedures which apply to clinical chemistry involve potentiometry, polarography, amperometry, coulometry, and conductometry. Potentiometry is one of the more widely used electrochemical analytical techniques. In potentiometry, the electrode potential difference between two electrodes in an electrochemical cell is measured. Many procedures involve measuring the change in electric potential over a period of time. In addition, a wide variety of ion-specific electrodes, as well as specialized electrolyte solutions, have been developed. Electrochemistry procedures are available for measuring a wide variety of ions present in biological fluids, including sodium, potassium, chloride, fluoride, and calcium ions.
Major consideration in designing analytical equipment for use by healthcare personnel is the amount of sample available for testing. In many situations, the amount of blood or other bodily fluid available is relatively small. Accordingly, there has been a trend in clinical chemistry to develop analytical systems which are capable of conducting numerous different chemical analyses on relatively small amounts of sample. In general, the goal has been to develop clinical analytical systems which provide the maximum number of medical tests utilizing the minimum amount of sample.
In achieving the above goals, a multitude of different analytical procedures and approaches have been investigated. In one approach, instruments have been developed which have a single sample introduction site. The equipment is designed so that the sample is split and routed to various locations within the system where multiple chemical analyses take place. Other systems do not include internal sample splitting devices and rely on the clinical chemist to separate the sample into small aliquots which are introduced into various instruments which are capable of conducting a maximum of only a few chemical analyses at one time.
In the field of clinical electrochemistry, a number of devices have been developed for determining the ionic activity in relatively small amounts of fluid (i.e. 10-50 .mu.l). Such devices generally include a plurality of ion-selective solid electrode pairs which are associated with liquid distribution porous membranes and a porous capillary bridge which are oriented to provide electrical conduction between the two electrodes when the test solution and reference solution are spotted onto the porous members. The electrodes and porous members are housed in a support frame which includes covers having apertures through which liquid is introduced into the device. These multiple electrode devices are used to simultaneously determine ionic activity of different ions in test solutions such as whole blood, plasma, serum and urine. These types of devices are disclosed in U.S. Pat. Nos. 4,437,970; 4,865,698; 4,528,085; 4,510,035; 4,655,899; 5,626,740; 4,555,274; 4,571,293; 4,615,788; 4,684,445; 4,871,441; and 5,021,140. These patents are all assigned to Fuji Photo Film Company, and the contents of each patent is hereby incorporated by reference.
There is a continuing need to develop and provide clinical chemistry equipment which is not only accurate, but versatile enough to meet the demands of modern medicine. The equipment should be simple enough to be used by not only highly-skilled laboratory technicians, but also by other healthcare personnel who may be required to conduct laboratory tests from time to time. The equipment and procedures should be versatile enough so that they can be utilized in clinical laboratories which analyze thousands of samples daily, while at the same time being adaptable to doctors' offices, home healthcare agencies and nursing homes where the number of tests being conducted is not as great. In addition, the equipment should be versatile enough to be useful in conducting a wide variety of electrochemical analyses which are presently being routinely utilized. The equipment should also be adaptable to conducting electrochemical analyses for blood or other bodily fluids which will be developed in the future.